There are literally two things you can do in this game other than watch the ducks: quack and fly.

To switch between ducks, press the 'Tab' button. You can press 'E' to switch camera modes.

To quack, click your left mouse button. Some of the ducks have unique quacks so be sure to try it out on multiple.

To jump, select a duck and press 'P' on your keyboard. To fly, press it repeatedly.

That's all the controls you need to know. Sit back and enjoy your duckies. :)